FUNDAMENTALS of SPUN YARN TECHNOLOGY Carl A Lawrence, Ph.D CRC PR E S S Boca Raton London New York Washington, D.C © 2003 by CRC Press LLC Library of Congress Cataloging-in-Publication Data Lawrence, Carl A Fundamentals of spun yarn technology / Carl A Lawrence p cm Includes bibliographical references and index ISBN 1-56676-821-7 (alk paper) Spun yarns Spun yarn industry Textile machinery I Title TSI480.L39 2002 677′.02862—dc21 2002034898 CIP This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials or for the consequences of their use The consent of CRC Press LLC does not extend to copying for general distribution, for promotion, for creating new works, or for resale Specific permission must be obtained in writing from CRC Press LLC for such copying Direct all inquiries to CRC Press LLC, 2000 N.W Corporate Blvd., Boca Raton, Florida 33431 Trademark Notice: Product or corporate names may be trademarks or registered trademarks, and are used only for identification and explanation, without intent to infringe Visit the CRC Press Web site at www.crcpress.com © 2003 by CRC Press LLC No claim to original U.S Government works International Standard Book Number 1-56676-821-7 Library of Congress Card Number 2002034898 Printed in the United States of America Printed on acid-free paper Dedication to Mary © 2003 by CRC Press LLC Preface The fundamentals of spun-yarn technology are concerned with the production of yarns from fibers of discrete lengths and the structure-property relation of the spun yarns Ever since humans moved from using the skins of hunted animals for clothing to farming and using farmed animal hairs and fibers from nonfood crops, and eventually to the manufacture of synthetic fibers, the spinning of yarns has been of importance to (initially) the craft and (subsequently) the science, design, and engineering of textiles This book is aimed at giving the reader a good background on the subject of the conversion of fibers into yarns, and an in-depth understanding of the principles of the various processes involved It has become popular among some textile technologists to view the subject area as yarn engineering, since there are various yarn structures that, with the blending of different fiber types, enable yarns to be constructed to meet specific end uses It is therefore necessary for the yarn engineer to have knowledge of the principal routes of material preparation and of the various modern spinning techniques These topics are covered in this book A distinction is made between the terms spinning method and spinning technique by referring to a technique as an implementation of a method, and thereby classifying the many techniques according to methods The purpose is to try to get the reader to identify commonality between spinning systems, something that the author has found useful in carrying out research into new spinning techniques With any mass-produced product, one essential requirement is consistency of properties For yarns, this starts with the chosen fiber to be spun The yarn technologist has to understand the importance of the various fiber properties used in specifying raw materials, not just with regard to the relation of fiber properties to yarn properties, but especially with respect to the effect of fiber properties on processing performance and yarn quality These aspects are given careful consideration in various chapters throughout the book An understanding of the meaning yarn quality is seen to be essential; therefore, some effort is devoted to explaining the factors that govern the concept of yarn quality Textile designers prefer to use the term yarn design rather than yarn engineering, since the emphasis is often on the aesthetics imparted to the end fabric as opposed to any technical function Fancy or effect yarns, blends of dyed fibers of different colors, and the plying together of yarns are important topics in yarn design, and the principles and processes employed are described in this book The material presented is largely that delivered over many years of lecturing and is arranged to be suitable for readers who are new to the subject as well as those who are familiar with the technology and may wish to use this book as a reference source A basic knowledge of physics and mathematics will be helpful to the reader, but is not essential, since a largely descriptive approach has been taken for the © 2003 by CRC Press LLC majority of the chapters The few chapters that may be considered more mathematically inclined present a more detailed consideration to a particular topic and should be easily understood by anyone who has studied physics and mathematics at the intermediate level Chapter gives a suitable introduction to the subject area by outlining much of the basic concepts and discussing what technically constitutes a spun yarn Chapters 2, 3, 5, 6, 7, and should cover most topics studied by technology students up to graduate level, and Chapter collates material that has been delivered as a module component largely to design students Chapters and 8, and some areas of Chapter that deal with yarn structure-property relation, have been used as topics within a Masters-level module Although, at the advanced level of study, programs are mainly based on current research findings, some areas of the earlier chapters may prove useful for conversion candidates Throughout the book, definitions are used, where appropriate, in an attempt to give the reader a snapshot of a particular technical point or topic, which is then explained in greater detail It is said that a picture is worth a thousand words, and in dealing with technical concepts, this is a truism The reader will find, therefore, that effort has been given to fully illustrating the substance of each chapter, and the author hopes that this makes the book a pleasant read for you © 2003 by CRC Press LLC Author Carl Lawrence, B.Sc (Applied Physics), Ph.D., is Professor of Textile Engineering at the University of Leeds and was previously a Senior Lecturer at the University of Manchester Institute of Science and Technology Before joining academia in 1981, he worked for 11 years in industrial R&D Many of these years were with the former Shirley Institute, now the British Textile Technology Group (BTTG) In 2002, he was awarded The Textile Institute’s Warner Memorial Medal for his contributions to investigations in textile technology — in particular, unconventional spinning systems He is the author of many research papers in the field of yarn manufacture and has several patents in the area of open-end spinning © 2003 by CRC Press LLC Acknowledgments I wish to express my appreciation to the many companies and individuals who gave me advice, encouragement, and assistance in completing this demanding but enjoyable project A special “thank you” to my research colleague and friend Dr Mohammed Mahmoudhi for his time and effort in preparing the majority of the diagrams in this book The following companies provided me the opportunity to include many of the illustrations depicted, for which I am very grateful: Andar ADM Group Ltd Befama S.A Crosrol Ltd ECC Ltd Fehrer AG Fleissener GmbH & Co Fratelli Mazoli & Co SpA Houget Duesberg Bosson Marzoli Melliand Pneumatic Conveyors Ltd Repco ST Rieter Machine Works Ltd (Machinenfabrik Rieter) Rolando Macchine Tessili Rolando-Beilla Saurer-Allma GmbH Savio Macchine Tessili SpA Spindelfabrik Suessen The Textile Institute (Journal of the Textile Institute) TRI (Textile Research Journal) Trutzschler GmbH & Co KG W Schlafhorst AG & Co William Tatham Ltd Zellweger Uster Zinser C A Lawrence University of Leeds © 2003 by CRC Press LLC Table of Contents Chapter Fundamentals of Yarns and Yarn Production 1.1 Early History and Developments 1.2 Yarn Classification and Structure 1.2.1 Classification of Yarns 1.2.2 The Importance of Yarns in Fabrics 1.2.3 A Simple Analysis of Yarn Structure 1.2.3.1 The Simple Helix Model 1.3 Yarn Count Systems 1.3.1 Dimensions of a Yarn 1.4 Twist and Twist Factor 1.4.1 Direction and Angle of Twist 1.4.2 Twist Insertion, Real Twist, Twist Level, and False Twist 1.4.2.1 Insertion of Real Twist 1.4.2.2 Twist Level 1.4.2.3 Insertion of False Twist 1.4.3 Twist Multiplier/Twist Factor 1.4.4 Twist Contraction/Retraction 1.5 Fiber Parallelism 1.6 Principles of Yarn Production 1.7 Raw Materials 1.7.1 The Global Fiber Market 1.7.2 The Important Fiber Characteristics and Properties for Yarn Production 1.7.2.1 Cotton Fibers 1.7.2.1.1 Fiber Length (UHM) 1.7.2.1.2 Length Uniformity Index (LUI) 1.7.2.1.3 Fiber Strength 1.7.2.1.4 Micronaire 1.7.2.1.5 Color 1.7.2.1.6 Preparation 1.7.2.1.7 Leaf and Extraneous Matter (Trash) 1.7.2.1.8 Stickiness 1.7.2.1.9 Nep Content 1.7.2.1.10 Short Fiber Content (SFC) 1.7.2.2 Wool Fibers 1.7.2.2.1 Fineness 1.7.2.2.2 Fiber Length Measurements 1.7.2.2.3 Tensile Properties 1.7.2.2.4 Color 1.7.2.2.5 Vegetable Content, Grease, and Yield © 2003 by CRC Press LLC 1.7.2.3 1.7.2.4 1.7.2.5 1.7.2.2.6 Crimp, Bulk, Lustre, Resilience 1.7.2.2.7 Medullation Speciality Hair Fibers 1.7.2.3.1 Mohair 1.7.2.3.2 Types of Fleeces 1.7.2.3.3 Physical Properties 1.7.2.3.4 Cashmere 1.7.2.3.5 Physical Properties Silk Fibers 1.7.2.4.1 Waste Silk Manufactured Fibers [Man-Made Fibers (MMFs)] 1.7.2.5.1 Viscose Rayon and Lyocell 1.7.2.5.2 Polyamide (Nylon) 1.7.2.5.3 Polyester 1.7.2.5.4 Acrylic 1.7.2.5.5 Polypropylene References Appendix 1A Derivation of Equation for False-Twist Insertion 1A.1 Twist Equation for Zone AX 1A.2 Twist Equation for Zone XB Appendix 1B Fiber Length Parameters 1B.1 Staple Length 1B.2 Fiber Length Distributions 1B.3 CFD by Suter-Webb Chapter Materials Preparation Stage I: Opening, Cleaning, and Scouring 2.1 Introduction 2.2 Stage I: Opening and Cleaning 2.2.1 Mechanical Opening and Cleaning 2.2.2 Striking from a Spike 2.2.3 Beater and Feed Roller 2.2.4 Use of Air Currents 2.2.5 Estimation of the Effectiveness of Opening and Cleaning Systems 2.2.5.1 Intensity of Opening 2.2.5.2 Openness Value 2.2.5.3 Cleaning Efficiency 2.2.6 Wool Scouring 2.2.7 Wool Carbonizing 2.2.8 Tuft Blending 2.2.8.1 Basic Principles of Tuft Blending 2.2.8.2 Tuft Blending Systems 2.2.9 Opening, Cleaning, and Blending Sequence References © 2003 by CRC Press LLC Appendix 2A Reference Lubricants Chapter Materials Preparation Stage II: Fundamentals of the Carding Process 3.1 Introduction 3.2 The Revolving Flat Card 3.2.1 The Chute Feed System 3.2.2 The Taker-in Zone 3.2.3 Cylinder Carding Zone 3.2.4 Cylinder-Doffer Stripping Zone 3.2.5 Sliver Formation 3.2.6 Continuity of Fiber Mass Flow 3.2.7 Drafts Equations 3.2.8 Production Equation 3.2.9 The Tandem Card 3.3 Worsted and Woolen Cards 3.3.1 Hopper Feed 3.3.2 Taker-in and Breast Section 3.3.3 Intermediate Feed Section of the Woolen Card 3.3.3.1 Carding Section 3.3.4 Burr Beater Cleaners and Crush Rollers 3.3.5 Sliver and Slubbing Formation 3.3.5.1 Tape Condenser 3.3.5.2 Ring-Doffer Condenser 3.3.6 Production Equations 3.4 Sliver Quality 3.4.1 Cleaning Efficiency 3.4.1.1 Short-Staple Carding 3.4.1.2 Worsted and Woolen Carding 3.4.2 Nep Formation and Removal 3.4.2.1 Nep Formation 3.4.2.2 The Effect of Fiber Properties 3.4.2.3 Effect of Machine Parameters 3.4.2.4 Short Fiber Content 3.4.3 Sliver and Slubbing Regularity 3.5 Autoleveling 3.6 Backwashing References Recommended Readings on the Measurement of Yarn Quality Parameters Appendix 3A Card Clothing 3A.1 Metallic Wires: Saw-Tooth Wire Clothing 3A.1.1 Tooth Depth 3A.1.2 Tooth Angles 3A.1.3 Point Density © 2003 by CRC Press LLC D N F b a Detaching Nip Line Doffer Nipper Plate Nip Line Drawing Feed Line Lap Forming Combing Card Sliver Can FIGURE 5.20 Fiber configuration in relation to detachment reach their foremost position only fiber a will be detached The other fibers will be retained in the ribbon fringe by the top comb During the next cycle, the cylinder comb will remove them as part of the noil It can be easily reasoned that, if these fibers had their hooks leading rather than trailing, the cylinder comb would have straightened them prior to the detaching action, and the longer ones would have formed part of the combed sliver Drawn or gilled slivers should comprise mostly straightened fibers, but remaining hooked fibers must enter combing with their hooked ends leading The majority of hooks in the output sliver from a card are tailing (see Chapters and 4) Therefore, to reposition these to be leading when presented to the cylinder comb, there should be an even number of reversing processes between the card and the comb, as depicted in Figure 5.20.68–71 Consider the configuration of fiber b in the figure If the looped end became leading, it is likely that the actual fiber ends would be held by the nipper plates during the combing action of the cylinder comb, and if a projecting pin moved through the loop, the fiber would break Similar breakages may occur to fibers with other unfavorable configurations in the sliver feed, in particular to fibers interlaced with neighboring ones Fiber breakage in combing is strongly related to the degree of fiber parallelism in a sliver fringe Therefore, it is important that appropriate drawing or gilling be used in the preparation of the sliver input to combing For © 2003 by CRC Press LLC cotton fibers, the use of fixed flats in carding, followed by drawing, was found to have a significant effect on comber waste Mill trials72 have shown that, for the same machine settings, the percentage comber waste was reduced from 16.4 to 14.2%, and the resulting yarn properties were improved The fiber-pin interaction in combing has been studied by a number of researchers,73,74 and various techniques have been used to obtain an indication of likely pin forces present during combing It was found that, generally, when a pin enters a sliver fringe, the force required for the pin to move through the fringe rises to a peak value and then decays to zero as the pin passes through the fringe.74 This is an indication of the resistance to pin movement If the lengths of the nipped fibers in the fringe lie parallel to the motion of the pin, then the initial resistance to pin movement is largely the friction force arising from the sliding contacts with the fibers On meeting impurities, neps, and short fibers to be removed, the resistance increases, as the pin then has to push these obstructions along its path until they are dislodged from the fringe If these obstructions are not firmly held by other fibers, the increase in force will be negligible, and the peak pin force will be small If, however, fringe fibers are not parallel, and interlaced fibers or doubled fibers are held at the nip-line (as would be expected in a card sliver fringe), then the peak pinforce reaches a high level at which these fibers will either have disentangled or been extended to reach their breaking strain, resulting in increased noil The reported findings showed that peak pin force increased with (a) fringe density, because of increased interfiber friction; (b) fringe length, owing to the presence of more impurities, neps, and short fibers to dislodge from the fringe; and (c) a reduced number of drawing passages The top comb pin force has also been studied during detachment and found to be greater than forces associated with the front ratchet zone in gilling It is a contributing factor to fiber breakage Increasing the number of gilling passages, however, reduces the size of the top comb pin force Belin and Taylor75 found that the back-ratchet draft in gilling has a significant effect on the quantity of noil removed in combing A moderate draft should not cause breakage in gilling but can reduce the size of the pin force at the cylinder and top combs developed during combing Although lubricants [combing oils of 106 centistokes (cS) viscosity] are added after scouring to reduce breakage, a small amount of residual grease on wool fibers does assist in keeping noil levels to a minimum Sinclair and Wood76 relate increased noil in wool combing to an entanglement factor, which is a complex function indirectly involving the residual grease content They found that noil increases with residual grease content above 1% Belin83 reports 0.8% (measured by Soxhlet ether extraction) to be the optimal level of residual grease At higher levels, the tendency is for fibers to stick together, and lubrication is impaired at lower levels 5.3 CONVERSION OF TOW TO SLIVER A tow is a collection of approximately 300,000 continuous man-made fiber filaments kept in a parallel, untwisted form To convert tows into a sliver, the individual filaments must be cut or broken collectively into staple fibers of a specified length Conventionally, the tow is chopped to the required staple length and baled ready for © 2003 by CRC Press LLC opening, blending, carding, and drawing/gilling so as to be made into a sliver by any of the particular process routes for material preparation A much shorter process route, called tow-to-top, is to cut or break the filaments while retaining them in their straight, parallel state, thereby producing a linear assembly of staple fibers that is comparable to a drawn/gilled sliver Besides the commercial advantages, there are technical benefits, since the fibers avoid impact forces of, in particular, opening and carding that cause neps and the unwanted very short fibers In converting the tow, the ends of the resulting staple fibers obviously must not coincide so that sliver cohesion is obtained, and longer staples will give better cohesion for handing of the sliver Tow-to-top conversion is therefore mainly utilized in worsted/semi-worsted yarn production, and then largely for viscose, polyester, and acrylic fibers Two types of machine are used; cutting converters and stretch-breaking converters 5.3.1 CUTTING CONVERTERS A cutter converter basically comprises a feed creel, a cutting unit, a sliver-forming section, a crimping unit, and a sliver can delivery As supplied by the fiber manufacturer, the tows are within the range of 10 to 60 ktex, depending on fiber type, and are packaged in plaited form into boxes In the feed creel, the tows are tensioned over a series of bars, which straightens and spreads the filaments evenly across the width of the input to the cutter The input count to the machine may be up to 200 ktex Figure 5.21 shows the basic cutting technique A helical-blade cutting roller is pressured onto the tows as they pass over a hard, smooth, stainless steel roller The helical shape provides overlapping of the cut lengths for cohesion, and the pitch of the helix provides the staple length The gaps between cutting edges of the helical blade have a rubber-covered surface that prevents filament misalignment, which could result in undersized lengths caused by double cutting of filaments.77 The cut lengths are then consolidated and gilled to form the sliver To impart crimp to the fibers for improved cohesion, the sliver is passed through a stuffer box before being coiled into a sliver can Dull cutters can result in partially cut lengths or cause fusing of cut ends The slivers from converters, therefore, usually undergo two further gilling passages, which separate individual fiber lengths possibly fused together at one of their cut ends 5.3.2 STRETCH-BREAKING CONVERTERS These converters use the idea of extending, in a controlled manner, synthetic filaments to their breaking strain, polyester and acrylic tow being the principal raw materials When heat treated, the broken lengths of stretched filaments can be made to readily shrink to produce a highly bulked yarn The process has therefore become popularly used in the material preparation for the production of high-bulk acrylic yarns The main features of a stretch-breaking converter are shown in Figure 5.21 and comprise four stretching zones: an initial tensioning zone, followed by a heatedand a cooling zone, and finally the filament breaking zone The resulting silver is then stuffer-box crimped and further cooled before being coiled into a sliver can © 2003 by CRC Press LLC Cutting Roller with Projecting Helical Blades Cut Staple Fibers Continuous Filament Tow Smooth Anvil Roller Stretching Zone C D Heater Continuous Filament Tow In A Tensioning Zone E B Cooling (Air Flow and Water Cooled) Staple Out Breaking Zone FIGURE 5.21 Tow-to-top converters Filament tows, making a total linear density of around 70 ktex for polyester or 120 ktex for acrylic, are fed to the stretch breaker via a creel spreader The tows are initially tension between rollers (A) and (B) Rollers (B) and (C) stretch the tows with a draft (or draw ratio) of within 1.4 to 1.8, while they are heated to a temperature within the range of 120 to 170°C At a set draw ratio, the filament tenacity increases, and its potential shrinkage decreases with temperature Within a suitable operating range of draw ratios, when the heater temperature is constant, both tenacity and potential shrinkage increase with increased draw ratio It is reported78 that, in the stretch breaking of nylon 6.6 tows, depending on temperature and draw ratio, the tenacity of the broken filaments may be increased by 20 to 40%, extension 36 to 78%, and initial modulus 85 to 144% The chosen settings will depend on the required shrinkage and the ease of breaking filaments For the production of nonbulked, regular yarns, heating is unnecessary The filament must be well cooled before reaching the third stretching zone, which is between roller sets (C) and (D) To achieve this, air cooling and watercooled rollers (C) are used The final stretching of the tow to the breaking point of the constituent filaments is performed by the rollers (E), which are spaced to give the required mean fiber length Ideally, a random distribution of filament breaks would be anticipated, resulting in a narrow distribution of fiber lengths In practice, however, variations in filament alignment,84 tensile properties, and fineness cause a wider distribution than the ideal © 2003 by CRC Press LLC 5.3.3 PRODUCTION EQUATION The production rate, PR (kg/h), is given by: P R = V d × T t × 60 × E × 10 where –2 (5.12) Vd = delivery of sliver (m/min) Tt = sliver count (ktex) E = machine efficiency (%) 5.4 ROVING PRODUCTION For certain spinning processes, the drawn sliver count must be reduced in two steps so that, ultimately, an acceptable yarn quality is achieved Equation 5.5 shows that, with roller drafting, the output irregularity increases as the draft increases, owing to the more pronounced effect of the drafting wave Therefore, one benefit of a twostage drafting operation is that the reversal of the material length at the second stage provides, effectively, a reversal in the drafting direction of the fibers, and this tends to reduce the amount of bunching of short fibers to give a less pronounced drafting wave If, for example, we wished to spin a yarn of 30 tex from 1.5-dtex fibers, and the drawn sliver count is ktex, then the required draft of 100 would best be applied in two steps, typically and 20 It is necessary for the first step draft to be low because then only a low twist is needed to hold the fibers together There would be, on average, approximately 20,000 fibers in the 3-ktex sliver cross section The draft of would reduce this to 4000 fibers in the cross section, and a small amount twist would be needed to give the attenuated length sufficient cohesion for suitable handling Increasing the draft would require increasing the twist However, the inserted twist must not cause problems in the second drafting step by developing a high drafting force Since the drafted material of the second stage is to be substantial twisted to form a yarn, the greater draft should be applied in that spinning stage The first drafting step forms the final part of the sequence for preparing fibers for spinning The intermediate product is called a roving and is made either on twist inserting machines, known as roving-frames, speed-frames, or flyer-frames, or on machines, called rub-rovers, that employ a rubbing action instead of twist insertion to consolidate the attenuated fiber mass This latter system is suitable only for fiber lengths applicable to the worsted process, since sufficient cohesion is required for handling Definition: A roving is a continuous fibrous strand drafted from a sliver and given cohesion by either inserting a small amount of twist or compacting the fibers with an oscillating apron It is drafted and twisted to be spun into a yarn In the production of a roving, a 3-over-3 roller drafting system is commonly used to attenuate the sliver Unlike the drawing operation, the slivers are drafted © 2003 by CRC Press LLC separately and, since there are now fewer fibers in the cross section, alternative means to a pressure bar or pins are used for control of floating fibers.79–81 The most commonly used is the double apron drafting method, illustrated in Figure 5.22 As shown, this is a two-zone drafting arrangement in which a pair of endless aprons is positioned in the high-draft front zone and made to move at the surface speed of the middle-roller pair As fibers enter the high-draft front zone, the aprons will hold them and assist in keeping them moving at the surface speed of the middle rollers, while preventing the short-fibers being dragged forward by those fibers nipped and accelerated by the front rollers By comparing the speed profiles of the floating fibers, it can be seen that the distance over which the motion of the short-fibers is uncontrolled has been reduced, thereby minimizing the prominence of the drafting wave.9 Back Rollers Apron Apron Front Rollers Drafting Zone tb Roller Drafting System tf (y) Time (t) Apron Drafting System tb Drafting Zone (y) Time (t) FIGURE 5.22 Apron drafting control of floating fibers © 2003 by CRC Press LLC tf 5.4.1 THE SPEED-FRAME (TWISTED ROVINGS) Figure 5.23 shows a sideways illustration of a speed-frame, and Figure 5.24 shows an example of a commercial machine The main operating features are a 3-over-3 apron drafting system and a combined twist insertion and bobbin build mechanism The function of the apron drafting system has already been explained The operation of the twist-and-bobbin build device can be described with reference to the figure As shown, the device has a central spindle that passes through a second, but hollow, spindle Both are driven independently and pass freely through the rail, which traverses up and down a set distance along the length of the hollow spindle A bobbin tube, onto which the roving is wound, sheaths the hollow spindle and rests on a mount (bobbin mount) fitted to the rail The motion of the rail moves the bobbin up and down the hollow spindle length Mounted on the top end of the central spindle is a component known as the flyer This has a hollow leg through which the roving travels to the bobbing Located at the exit is a presser arm and paddle around which the roving slides along to the bobbin The arm is attached to a support rod, and, during rotation of the flyer, this rod is moved outward by centrifugal forces and thereby swivels the presser arm inward to guide the roving onto the bobbin tube The opposite leg of the flyer is solid and gives dynamic balance during spindle rotation As the flyer rotates with the centre spindle, twist is inserted into the drafted ribbon issuing from the front rollers of the drafting system, thereby forming the roving The contact between the roving and the rim of the flyer inlet imparts an added false twist (see Chapter 1), which strengths the roving length between the flyer and front drafting rollers, permitting a low value of real twist to be used The roving, which is threaded through the hollow of the fly and around the presser arm, is pulled and wound onto the bobbin by the rotation of the hollow spindle To so, the hollow spindle rotates at a higher speed than the center spindle, and the rail lifts and lowers the bobbin past the presser arm to build successive layers of roving coils and make a full bobbin This is often referred to as winding-up by bobbin lead If the bobbin rotates at speed Nb, and the spindle at Ns, then the speed, Vw , at which the roving would be wound onto the bobbin tube is given by Vw = π Db (Nb – Ns) (5.13) where Db = the bobbin tube diameter (in meters) at the instant of winding In the equation, Nb and Ns are in units of rpm, and Vw is in m/min Clearly, if the roving is not to break during winding, there must be a balance between the winding-up speed, Vw , and the delivery speed, Vd (m/min), at which the drafted ribbon leaves the front drafting rollers Therefore, as Db increases with the number of roving layers wound onto the bobbin, Nb must decrease, since Ns must be kept constant to ensure a constant twist level Two or three wraps of the roving around the pressure arm increases the winding-on tension This, in turn, contracts the roving diameter to enable more roving to be wound onto the bobbin © 2003 by CRC Press LLC Drafting System + + + + + Sliver + + Twisted Rowing Direction of Twist Spindle Collar Flyer + + Drive to Collar + Drive to Spindle + Spindle Fly Brass Bush Bobbin Support Rod Collar Twisted Roving Track to Aid Rail Movement Movement of Bobbin Rail Presser Foot Bobbin Rail + Bobbin Support with Bearing Bobbin Drive + Spindle Drive FIGURE 5.23 Basic features of a roving frame © 2003 by CRC Press LLC FIGURE 5.24 Basic roving frame It can be seen in Figures 5.23 and 5.24 that speed-frames are fitted with two rows of the flyer twisting device The level of false twist inserted by the flyer inlet is dependent on the contact angle of the roving length between the flyer and the front drafting rollers; the smaller the angle, the higher the false twist The back row of flyers is nearer the drafting rollers and therefore has the greater contact angle The lower false twist does not give sufficient cohesion to the roving length to prevent induced tensions reducing the roving count slightly In some cases, this difference can be significant and result in a difference in the yarn count produced from front and back rows of roving bobbins To prevent this, modern speed-frames have the back row flyer fitted with a raised false-twister attachment (see Figure 5.25) bringing the contact angles of the two row to almost similar values 5.4.1.1 Production Equation The production rate of a speed-frame is dependent on the spindle speed of the fly, the number of spindles per machine, the production efficiency, the roving count, and the twist multiplier used The following equation gives the calculated production rate © 2003 by CRC Press LLC Approach Angle without Raised Flyer Attachment Approach Angle with Raised Flyer Attachment FIGURE 5.25 Flyer attachment to counter count differences (Courtesy of Zinser Ltd.) FIGURE 5.26 Basic features of twistless roving frame –9 60 × 10 × E × n × N s T t – r P R = -TM where PR = production rate (kg/h) TM = twist multiple (turn m/tex) E = machine efficiency (%) n = number of spindle per machine © 2003 by CRC Press LLC (5.14) Ns = spindle speed (rpm) Tt – r = roving count (tex) 5.4.2 RUB ROVERS (TWISTLESS ROVINGS) The principle used to produce twistless rovings is similar to the production of woolen slubbings (see Figure 5.26) The drafted ribbon of fibers issuing from the doubleapron drafting system is threaded between a pair of oscillating aprons that roll and compress the ribbon of fibers into a round, consolidated, more cohesive, continuous length The twistless rovings are then wound with minimum tension onto a tube With the absence of twist the production rate becomes as shown below 5.4.2.1 Production Equation PR = 60 × 10–5 × Vd × n × Tt – r × E (5.15) 5.5 ENVIRONMENTAL PROCESSING CONDITIONS Figure 1.8 (Chapter 1) gives a flowchart of process routes for the production of carded and combed ring-spun yarns, rotor yarns, worsted and semi-worsted yarns, and woolen yarns Although some routes are relatively short, it is nevertheless true to say that fibers undergo a great amount of sliding contact between themselves and with machine surfaces The associated friction generates static charges and, being basically nonconducting, fibers retain and accumulate the charges and tend to cling to nonmetallic parts of machines, resulting in processing difficulties and faults in the output material.82 The heat developed during process operations will tend to reduce the moisture content of hygroscopic fibers, and, since moisture is an important means of conducting away static charges, the problem of static can increase with the number of processes There is also the risk that fibers will become more susceptible to breakage To minimize static problems, it is necessary to maintain the environmental conditions, in terms of percent relative humidity (%RH) and temperature, at levels that will retain adequate moisture in hygroscopic fibers Certain finishes are usually applied to man-made fibers as lubricants and to reduce the tendency for static charge buildup Nevertheless, it is still found necessary to have controlled %RH and temperature If, however, the humidity is kept too high, fibers may stick to metallic and nonmetallic surfaces Table 5.3 gives quoted values of %RH according to fiber type and process stage Wool is more hygroscopic than other fibers, so higher levels of relative humidity are used The moisture content is influenced by the condition of the wool (i.e., the presence of wool fats and oils, acids, and alkalies; the degree of compactness; and structural changes the fiber may undergo during processing, particularly scouring) However, within 70 to 80% RH and 21°C, the environment will keep the moisture in wool at between 15 and 18% regain, making it suitable for mechanical working Cellulose fibers develop much less static that protein fibers, so lower %RH levels (45 to 55%) but higher temperatures (up to 27°C) are used, particularly in the © 2003 by CRC Press LLC TABLE 5.3 Process Environmental Conditions for Fiber Types Process Cotton/regenerated cellulose Opening Carding Combing Drawing Roving Spinning Synthetics o C %RH o C %RH 23 23 27 25 25 27 55 50–55 42 48–50 48–50 48–50 27 27 27 27 27 27 40 40 – 45–65 40–45 35–40 Protein fibers o C %RH 18–23 18–23 18–23 18–23 18–23 18–23 66–80 65–80 65–80 70–80 50–60 50–60 Courtesy of P R Lord, Economics, Science & Technology, 1981, 172 preparatory process stages, as this also increases the elasticity of the fiber For synthetics, 35 to 60% RH and temperatures up to 27°C cover most levels used, with nylons being at the lower end of the %RH range, acrylic around the middle, and polyester at the higher end REFERENCES Cox, D R and Ingham, J., Some causes of irregularity in worsted drawing and spinning, J Text Inst., 41, 376, 1950 Grishin, P F., A theory of drafting 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Textil-Praxis, 23, 595, 1968 21 Arano, A., Some features of random slivers, J Text Inst., 47, P781, 1956 22 Wegener, W and Ehrier, P., Idealised drafting, Textil-Praxis, 25, 282, 346, 1970 23 Lamb, P R., The effect of spinning draft on irregularity and faults, part I: Theory and simulation, J Text Inst., 78(2), 88–100, 1987 and part II: Experimental studies, J Text Inst., 78(2), 101–111, 1987 24 DeLuca, L B., Hebert, J J., and Simpson, J A., A method for automating the west point cohesion tester, Text Res J., 35, 467–477, 1965 25 Martindale, J G., Cotton sliver or roving: Measurement of drafting force, J Text Inst., 38, T151, 1947 26 Plonsker, H R and Backer, S., The dynamics of roller drafting, part 1: Drafting force measurement, Text Res J., 37, 673–687, 1967 27 Taylor, D S., The measurement of fibre friction and its application to drafting force and fibre control calculations, J Text Inst., 46, 59–83, 1955 28 Olsen, J S., Measurement of sliver drafting forces, Text Res J., 852–835, 1974 29 Cavaney, B and Foster, G A R., Some observations on the drafting forces of cotton and rayon-staple slivers, Shirley Inst Memoirs, XXVII, 37–51, 1954 30 Bastawisy, A D., Onions, W J., and Townend, P P., Some relationships between the properties of fibres and their behaviour in spinning using the Ambler super-draft method, J Text Inst., 52, T1, 1961 31 Turpie, D W F., SAWTRI, Technical Report No 400, 1978 32 Green, J and Ingham, J., Technique for visualising the position of staple fibres in sliver and its application to drafting problems, J Text Inst., 43, T473, 1952 33 Postle, L J R., Ph.D thesis, Some measurements relating to the fibre friction forces acting during drafting, University of Leeds, UK, 1955 34 Grosberg, P A., The short-term irregularity of roller-drafted yarns and slivers, J Text Inst., 49, T493, 1958 35 Grosberg, P A., Cause of irregularity in roller drafting, J Text Inst., 52, T91, 1961 36 Grosberg, P A., Cause of irregularity in roller drafting, J Text Inst., 53, T533, 1962 37 Balasubramanian, H., Ph.D thesis, A study of the short-term irregularities in rollerdrafted materials using measurements of the variations in fibre-end density, University of Leeds, UK, 1964 38 Grosberg, P., J Text Inst., 76, 296, 1966 39 Dutta, B and Grosberg, P., The dynamic response of drafting tension to sinusoidal variations in draft ratio under conditions of sliver elasticity in short-staple drafting, J Text Inst., 64, 534, 1973 40 Grosberg, P and Yang, W.L., The Cause of Sliver Irregularity in Gilling, J Text Inst., 65, 20, 1974 41 Burte, H M., The properties of apparel wools, VII: The mechanical behaviour of roving, Text Res J., 24, 726, 1954 42 Dutta, B., Ph.D Thesis, Dynamic response and automatic control of short staple drafting, University of Leeds, UK, 1970 © 2003 by CRC Press LLC 43 Waggett, G., The tensile properties of card and drawframe slivers, J Text Inst., 43, T380–395, 1952 44 Grover, G and Lord, P R., The measurement of sliver properties on the drawframe, J Text Inst., 83(4), 560–572, 1992 45 Merchant, V B., Theoretical aspects of hook removal at drafting operations, Text Res J., 31, 925–930, 1961 46 Merchant, V B., Theoretical aspects of hook removal at drafting operations, part II: The influence of changes in draft distribution on the removal of trailing and leading hooks, Text Res J., 32, 805–810, 1962 47 Simpson, J and De Luca, L., Effect of sliver weight entering drawing on fibre hook removal, Text Res J., 35, 675–676, 1965 48 Nutter, W., Removal of fibre hooks by roller drafting, Text Res J., 32, 430–431, 1962 49 Ghosh, G C and Bhaduri, S N., Dependence of hook removal at drawing on some drafting parameters, Text Res J., 32, 864–866, 1962 50 Hertel, K L and Craven, C J J., Determination of floating fibres, Textile Industries, 124, 103–107, 1960 51 Prakash, J., Estimation of floating fibre percentage using the digital fibrograph, Text Res J., 62, 244–245, 1962 52 Waggett, G., The tensile properties of card and drawframe slivers, J Text Inst., 43, T380–395, 1952 53 Fibrograph Determination of Draft Roll Space Settings, Spinlab Utility Instrumentation, Inc., Knoxville, TN 54 Hattenschwiler, P and Eberle, H., Quality in staple fibre spinning: Practical examples, Melliand Textilberichte, 1987 55 King, E., The Role of the Modern Drawframe, Int Text Bull., Yarn Forming, 1, 35–45, 1991 56 Foster, G A R., Manual of cotton spinning: Drawframes, combers, and speedframes, Chap 2, The Textile Institute, Manchester, UK, 1958 57 Klien, W., Manual of Textile Technology — Short-Staple Spinning Series: A Practical Guide to Combing and Drawing, Vol 3, Chap 2, The Textile Institute, Manchester, UK, 1987 58 Quality assurance with various spinning systems, Uster News Bulletin, 32, 1–31, 1984 59 Tautenhahn, K and Schmauser, E M, Basic principles for determining the pinning of faller bars on gill boxes, Int Text Bull Yarn Forming, 1(66), 1984 60 Belin, R E., Hooked fibres in carding and gilling, J Text Inst., 64, 659–664, 1973 61 Grosberg, P and Yand, W L., The cause of sliver irregularity in gilling, J Text Inst., 65, 20–26, 1974 62 Yang, W L, An Investigation into the Causes of Sliver Irregularity in the Gill Boxes, Ph.D thesis, University of Leeds, UK, 1970 63 Taylor, D S., The motion of floating fibres during drafting of worsted slivers, J Text Inst., 46, T284, 1955 64 Tautenhahn, K and Schmauser, E M, Basic principles for determining the pinning of faller bars on gill boxes, Int Text Bull Yarn Forming, 1(66), 1984 65 Gruarin, R., Inter-linking of lap preparation, combing and drawing — A modern logistical solution, Int Text Bull., 3, 28–34, 1994 66 Bird, C L., The Theory and Practice of Wool Dyeing, 4th ed., Society of Dyers and Colourists, Bradford, UK, 1972 67 Wakeham, H., Cotton fibre length distribution — An important quality factor, Text Res J., 25, 422–429, 1955 © 2003 by CRC Press LLC 68 Belin, R E and Taylor, D S., Directional effects in worsted rectilinear combing, J Text Inst., 58, 145–157, 1967 69 Wankankar, V A and Bhaduri, S N., The effect of fibre configuration in feed on comber waste, Text Res J., 32, 641–651, 1962 70 Leont’eva, L S., Problem of fibre straightening during sliver preparation, Technology of Textile Industry, USSR, 2, 57–63, 1964 71 Simpson, J., Comparison of the combing and cutting ratios as an indication of fibre arrangement, Text Res J., 32, 614–615, 1962 72 Grimshaw, K., Benefits for cotton system from the use of fixed carding flats, Conference Proc.: Tomorrow’s Yarns, 26–28 June, 166–181, 1984 73 Kruger, P J., Withdrawal forces in the processing of wool slivers, part I: The determination of withdrawal force, J Text Inst., 59, 463–471, 1967; part II: The influence of variations in gilling on the withdrawal force, J Text Inst., 59, 472–477, 1967; and part III: The influence of pin-density variations, J Text Inst., 59, 478–486, 1967 74 Johnson, N A G and Wang, X., Investigation of combing forces, part I: Fibre tension, J Text Inst., 82(3), 399 –408, 1991, and part II: Pin forces, J Text Inst., 82(3), 120–126, 1992 75 Belin, R E and Taylor, D S, The effect of backdraft applied at the first gilling operating after worsted carding, J Text Inst., 60, 132–139, 1969 76 Sinclair, J F and Wood, G F., An apparatus for measuring fibre entanglement in scoured wool and some applications in scouring investigations, J Text Inst., 56, T274–T279, 1965 77 Wagget, G., The relation between the orientation of filaments in a rayon tow and some characteristics of tops made from tow, J Text Inst., 45, T81–T91, 1954 78 Watt, J D., Some changes in filament and fibre load-extension characteristics which result from stretch-breaking Nylon 6.6 on a Seydel machine, J Text Inst., 52(7), T303–T308, 1961 79 Oxtoby, E., Spun Yarn Technology, Chap 5, Butterworth-Heinemann, Boston, MA, 1987, 58–61 80 Balasubramanian, N., Upgrading by apron drafting, Text Res J., 32, 957–958, 1962 81 Fujino, K., Shimotsuma, Y., and Fujii, T., A study of apron-drafting, part I: Experimental studies, J Text Inst., 2, 50–59, 1977, and part II: A theoretical analysis of floating fibre control, J Text Inst., 2, 60–68, 1977 82 Pillay, K P R., Effect of ambient atmospheric conditions during spinning on yarn properties and spinning efficiency, Text Res J., 41(1), 11–15, 1971 83 Belin, R E., Residual grease in the gilling and rectilinear combing of merino wool, J Text Inst., 58, 169–174, 1967 84 Wagget, G., The relation between the orientation of filaments in a rayon tow and some characteristics of tops made from tow, J Text Inst., 45, T81–T91, 1954 © 2003 by CRC Press LLC [...]... 6 .1. 1.5 Spun- Plied Spinning 6 .1. 1.6 Key Points 6 .1. 1.6 .1 Advantages 6 .1. 1.6.2 Disadvantages 6 .1. 2 Open-End Spinning Systems 6 .1. 2 .1 OE Rotor Spinning 6 .1. 2 .1. 1 Twist Insertion 6 .1. 2 .1. 2 End Breaks during Spinning 6 .1. 2.2 OE Friction Spinning 6 .1. 3 Self-Twist Spinning System 6 .1. 4 Wrap Spinning Systems 6 .1. 4 .1 Surface Fiber Wrapping 6 .1. 4 .1. 1 Dref-3 Friction Spinning 6 .1. 4 .1. 2 Air-Jet Spinning 6 .1. 4 .1. 3... Model of Yarn Structures 6.2.2 Formation of Spun Yarn Structures 6.2.2 .1 Conventional Ring -Spun Yarns 6.2.2 .1. 1 Mechanism of Fiber Migration 6.2.2.2 Compact Ring -Spun Yarns 6.2.2.3 Formation of Rotor Yarn Structure 6.2.2.3 .1 Cyclic Aggregation 6.2.2.3.2 Theory of Spun- in Fibers in Yarns 6.2.2.4 Formation of Friction -Spun Yarn Structures 6.2.2.5 Formation of Wrap -Spun Yarn Structures 6.2.2.5 .1 Air-Jet Spun. .. III 5 .1 Drawing 5 .1. 1 Principles of Doubling 5 .1. 2 Principles of Roller Drafting 5 .1. 2 .1 Ideal Drafting 5 .1. 2.2 Actual Drafting 5 .1. 2.2 .1 Effect of Input Material Characteristics 5 .1. 2.2.2 Drafting Wave 5 .1. 2.2.3 Observations of Floating Fiber Motion 5 .1. 2.2.4 Drafting Force 5 .1. 2.3 Factors Influencing Drafting Wave Irregularity 5 .1. 2.3 .1 Size of Draft 5 .1. 2.3.2 Input Count 5 .1. 2.3.3 Doubling 5 .1. 2.3.4... Nm New Ny 1 kg 1 lb 1 lb Standard length unit Equivalent tex 1 km 10 km 10 00 km 1m 9 km 1 0 .1 0.0 01 1000 0 .11 11 840 yd (1 hank) 1 km 560 yd 256 yd (1 skein) 590.5 10 00 885.8 l938 Although all the units of count in Table 1. 3 are used in practice, we shall use only the tex throughout the remaining chapters of this book The table gives the conversion factors in relation to tex A clear advantage of the tex... and Length 5 .1. 2.3.5 Roller Settings 5 .1. 3 Effect of Machine Defects 5 .1. 3 .1 Roller Eccentricity 5 .1. 3.2 Roller Slip 5 .1. 4 The Drawing Operations 5 .1. 4 .1 The Drawframe 5 .1. 4.2 The Gill Box 5 .1. 5 Production Equation 5.2 Combing 5.2 .1 The Principles of Rectilinear Combing 5.2 .1. 1 Nasmith Comb 5.2 .1. 1 .1 The Cylinder Comb 5.2 .1. 1.2 The Feed Roller/Top and Bottom Nipper Plates/Top Comb 5.2 .1. 1.3 Detaching... fractions of the tex in terms of the base 10 scale Thus, 10 00 tex = 1 kilotex (ktex), 0 .1 tex = decitex (dtex), and 0.0 01 tex = millitex (mtex) In this way, the tex unit can be used for fibers and yarns Hence, if we have a yarn of 10 0 tex spun from fiber of 1 dtex (0 .1 tex), we can estimate the number of fibers in the yarn cross section to be 10 00 A 50-tex yarn should be half the size of a 10 0tex, requiring... Rovings) 5.4 .1. 1 Production Equation 5.4.2 Rub Rovers (Twistless Rovings) 5.4.2 .1 Production Equation 5.5 Environmental Processing Conditions References Chapter 6 Yarn Formation Structure and Properties 6 .1 Spinning Systems 6 .1. 1 Ring and Traveler Spinning Systems 6 .1. 1 .1 Conventional Ring Spinning 6 .1. 1.2 Spinning Tensions 6 .1. 1.3 Twist Insertion and Bobbin Winding 6 .1. 1.3 .1 Spinning End Breaks 6 .1. 1.4 Compact... are three ways of constructing an answer to this question: • To present a classification of yarns • To look at the importance of yarns in fabrics • To analyze various yarn structures and identify their most common features 1. 2 .1 CLASSIFICATION OF YARNS Table 1. 1 shows that yarns may be classified into four main groups: continuous filament, staple spun, composite, and plied yarns TABLE 1. 1 Yarn Classification... 6 .1. 4.2 Filament Wrapping 6 .1. 5 Twistless Spinning Systems 6 .1. 5 .1 Continuous Felting: Periloc Process 6 .1. 5.2 Adhesive Bonding: Bobtex Process 6 .1. 6 Core Spinning 6 .1. 7 Doubling Principles 6 .1. 7 .1 Down Twisting 6 .1. 7.2 Two-for-One Twisting 6 .1. 8 Economic Considerations © 2003 by CRC Press LLC 6.2 Yarn Structure and Properties 6.2 .1 Yarn Structure 6.2 .1. 1 Surface Characteristics and Geometry 6.2 .1. 2... Machines 7.2 .1. 1 Wing Cam © 2003 by CRC Press LLC 7.2 .1. 2 7.2 .1. 3 7.2 .1. 4 7.2 .1. 5 Grooved Drum Patterning/Ribboning Sloughing-Off Anti-patterning Devices 7.2 .1. 5 .1 Variation of Traverse Frequency, Nt 7.2 .1. 5.2 Variation of Drum Speed, Nd 7.2 .1. 5.3 Lifting of Bobbin to Reduce Nb 7.2 .1. 5.4 Rock-and-Roll Method 7.2.2 Precision Winding Machines 7.2.3 Advantages and Disadvantages of the Two Methods of Winding